Plastic composition, film, or article and process of making the same



Patented Jan. 26, 1932 ADOLPH ZIMMERLI, OF NEW BRUNSWICK, NEW JERSEY, ASSIGNOR TO ACETOL PRODUCTS, INC., A CORPORATION OF DELAWARE PLASTIC COMPOSITION, FILM, OR ARTICLE AND PROCESS OF MAKING THE SAME No Drawing.

This application is in part a continuation of In prior application, Serial No. 7 00,733, filed arch 20, 1924 and assigned to Acetol Products, Inc.

My invention relates to a plastic composition, applied in the form of a lacquer, capable of forming, when hardened, a thin transparent film. More particularly the invention relates to a composition of this character having the ability to pass ultraviolet light. A further feature of the invention resides in the method of applying the lacquer in the treatment of wire fabric.

It is an object of my invention to provide a composition comprising a film-forming substance which, when hardened, is capable of transmitting ultraviolet light in the region most beneficial biologically.

Another object is the provision of a plastic composition which not only passes the ultraviolet rays but which also resists discoloration when exposed to weather conditions.

Another object of the invention is the provision of a composition of this character which may be applied to a wire fabric and having the properties of being highly resistant to atmospheric conditions, a predetermined elasticity, ability to adhere to metal and is a poor conductor of heat.

Another object of the invention is the provision of a method of effecting the uniform distribution of a film-forming substance over the surface of a wire fabric by maintaining the viscosity of the substance constant and drying the coated fabric in the vapor of the solvent.

Ever since Spengler, Rollier, Bernhard and others had shown that sunburn had a beneficial effect on the resistance of the body towards bacterial infection, the effect of sun light and of artificial light on animallife in general has been studied extensively. It took a long time, however, until it was discovered that the beneficial effect is due to a specific action of a. very narrow band in the ultraviolet spectrum.

Following this discovery there has been a great deal of activity in investigating the physiological action of ultraviolet light. Various artificial sources of ultraviolet light thereby causing severe burns.

Application filed February 9, 1928. Serial No. 253,226.

Therapy of the American Medical Association has cautioned the public against using such devices and condemned the sale thereof for a number of reasons, chief of which is that unless proper precautions are observed in administering ultraviolet treatments severe o0 burns and grave injury to the eyes may result (Journal of the American Medical Association), January 22, 1927, vol. 88, No. 4, page 245 It is the short rays of ultraviolet light that are harmful. They are absorbed by the outer layers of the skin which they destroy rapidly, For this reason they are not only useless, but very dangerous and inasmuch as the ultraviolet spectrum through quartz extends from 4,000 to 2,000 Angstrom units a quartz mercury vapor lamp should not be used as a light source without proper filters.

It has been found that the beneficial rays in the prevention of rickets lie between 3200 and 2800 A. Therefore, in order to be of the greatest. value in the prevention and cure of rachitic conditions a light source should not emit any rays shorter than 2800 A. The

suns ultraviolet spectrum does not include waves shorter than 2970 A. and the sun is the only light source known to fulfill this condition. Rays longer than 3200 A. are not harmful but have no appreciable physiological value.

It would therefore seem that the only common and safe source of ultraviolet light is sunlight. However, it is a well known fact that ordinary window glass does not transmit ultraviolet light of wave lengths shorter than 3200 A. Recently efi'orts have been made to produce window glass which will transmit these short ultraviolet rays of the sun. manufacture and very expensive, so that it is extremely doubtful whether they may come into general use.

Fortunately there are now onthe market certain products sold as substitutes for win- 1190 However, these glasses are difficult to dow glass. These substitutes comprise a base material, such as a Wire or cloth fabric, coated or impregnated with a water-proof coating. One such product is exploited under the trade-mark Cel-O-Glass and is covered by Oolle et al. Patent No. 1,580,287, issued April 13, 1926 and controlled by .Acetol Products, Inc. In the case of Cel-O-Glass the base is a wire fabric, coated with a composition comprising a thin, transparent film which completely incases the strands of the base material, but is of such a thickness as to be substantially subdivided into sections corresponding in number and general design to the meshes of the base.

In the manufacture of such window glass 7 substitutes the coating material is comprised of organic substances. There are great variations in the transparency of organic substances to ultraviolet radiation of difierent wave lengths. Some get gradually more opaque as the rays get shorter, while others are more or less uniformly transparent to a certain wave length at which they become opaque quite suddenly. Others still have one or more absorption bands at certain wave lengths and are transparent for. longer as well as for shorter waves.

I have found that by adding a suitable plasticizer in a certain proportion to a cellulose acetate solution in a volatile solvent, there remains after-drying a film which highly transparent to ultraviolet rays in the most desirable region, that is between 3200 and 2800 A. but which is opaque for rays shorter than 2800 A.

- I am aware that it has been common in the prior art to use a coating composition, in the treatment of reticulated materials, compriscellulose acetate dissolved in some suitable solvent. A film formed from such a a solvent is transparent, quite stable and resistant to weather conditions. Such a film, however, is not elastic enough and shows no adherence to metal. Therefore, in order to satisfactorily coat a reticular metallic material, such as a wire cloth or screen, it be comes necessary to employ an agent capable of imparting these properties, and consequently plasticizers are resorted to. If an.

, coating may become opaque in some instances,

and brown in others.

I employ the term actinic. in the sense of,chemically active. his not exactlyidentical with physiologically active but broader and includes practically all of the ultravioletrays of the sun Percy Hall in his book, Ultraviolet Rays in the Treatment 7 and Cure of Disease (O. V. Mosby 00., St.

Louis, 1924) gives this definition on page 7 The ultraviolet rays are actinic or chemi- I calraysso called because of the chemical changes they produce if allowed to fallupon sensitive media, such as photographic plates.

E. C. Ernst in the introduction -to the American edition of Pgpcy I-Ialls book (supra) on page 1 refers o: The invisible ultraviolet or actinic rays of the suns spectrum It is a general rule that with shorter wave lengths corresponding to more rapid vibration the chemical activity grows so that in sunlight the shortest wave lengths are the most active chemically as well as physiologically. In other words, while not all the actinic rays have a physiological action the most active rays of the suns spectrum are identical with the rays most beneficial biologically and any change which impairs the transmission of such rays detrimentally aifects'a very important or vital feature of translucents of the character of Cel-O-Glass. The significance of the term actinic will be more fully appreciated by further discussion elsewhere herein.

Other plasticizers melt under the influence are formedin the film. Again, others are disthin as a Spiderweb. Still, other plasticizers become brittle in cold weather, so that the wind cracks the film or coating formed from the solution. In order to overcome all of these objections it has, therefore, been no easy task to find a suitable plasticizer and todetermine its proportion so as not to weaken the film and still make it elastic and sufficiently adherent.

Besides giving considerable care to the selection of a proper or suitable plasticizer, it is important to employ a satisfactory solvent. In the past, it has been the practice to use a mixture of low and high boiling solvents. Although low boiling solvents may have been recognized as being preferable in making cellulose acetate solutions, on account of such matter disclosed in myPatent N 0. 1,613,073,

issued January 4, 1927 and controlled by Acetol Products, Inc, 1

In practicingmy invention, I may use cellulose acetate which is soluble in acetone or methylacetone to which has been added a.

suitable plasticizer. I prefer to employ diethylphthalate for this purpose, inasmuch as solved by rain, whereby the film becomes as it imparts to the resulting composition, the

above mentioned characteristics; namely,

weather resisting properties, ability to wet or adhere to metal and follow the expansion and contraction thereof. Diethylphthalate also possesses the property of transmitting the ultraviolet rays of the suns spectrum.

I have secured excellent results in using these substances in the following proportions:

Formula N 0. 1

Cellulose acetate, about 72 pounds Diethylphthalate, about 28 pounds Light solvent, about 100 gallons Formula 1V 0. 2

' Per cent Acetone 100-34 Benzene 0-33 Alcohol 0-33 If a greater quantity of benzene and/or alcohol are used. the dissolution of the solvent is prevented.

If methylacetone is employed for the solvent, it may be diluted by the following ingredients with the proportions as indicated:

Formula N 0. 3

' Per cent Methylacetone 100-50 Benzene 0-25 Denatured alcohol 0-25 The quantities of benzene and/or alcohol should not exceed the limits indicated or the applied to a reticular metallic base in any.

suitable manner, such as flowed or brushed thereon, but I prefer to use a machine of the type disclosed in my aforesaid Patent No. 1,613,073, wherein the wire cloth or netting comprising the metallic base material is taken off of a reel and passed through the coating solution, thence through a saturation and drying chamber, respectively, over a sys tem of rolls to insure an even speed or movement through the apparatus and finally rolling it up when dried. The drying chamber being closed and heated with radiant heat, avoid any difficulty from the standpoint of hygroscopicity of the solvent employed. By concentrating the vapors of the solvent immediately above the container for holding the coating solution the premature drying, or irregular setting, of the coating is prevented and there is afforded an opportunity for the coatingmaterial to distribute itself uniformly over the surface of the base material before it becomes hardened or set.

The consistency of the coating solution is such, that it readily attaches itself in a thin layer to the reticular metallic base, wetting the strands thereof and when dried, forms a thin transparent elastic film which does not crack or is deleteriously affected by weather conditions. By taking suitable precautions during the coating operation, the viscosity of the coating material may be maintained constant under varying weather conditions, such as temperature and barometric changes which may prevail from time to timewithin the room in which the coating process is car ried out. It is submitted that in order to secure uniformity in the quality of the product being manufactured according to this process it is necessary to compensate for, or regulate, the viscosity of the coating solution and any means which willinsure a constant viscosity of the solution may be employed for this purpose.

It may be opportune to mention here that the thicker the film resulting from the evaporation of the coating solution themore it absorbs the ultraviolet rays, so that in order to obtain a maximum .transmission of these rays it is desirable that the film be as thin as is consistent with other factors such as durability, etc. v By restricting the thickness of the film to that specified in the aforesaid Colle patent I have beenable to obtain excellent resultsboth as to life of the product and its ability to transmit the beneficial rays of any ultraviolet light source, particularly of sunlight.

From the foregoing, it is apparent that although cellulose acetate alone is known tobe capable of forming a transparent film, this film is-brittle and not elastic enough to follow the expansion and contraction of the strands of a reticular metallic material to which it may have been applied. Further, that although it may have been the .practice to employ plasticizers to produce elasticity in films and in plastic masses, nobody as far as I am aware, has ever attempted to produce a solution of cellulose acetate with such an amount of a plasticizer as to form a composition of matter on evaporation of the solvent, that will be resistant to the elements and follow the expansion and contraction of a reticular wire base or screen. There are few plasticizers known to have these valuable properties. The great majority of them are either not re sistant to direct sunlight or heat or rain or freezing, or they do not adhere to and follow the expansion and contraction of a metallic base to which they have been employed. Furthermore, most plasticizers are not adapted to transmit the ultravoilet rays and although they may possess weather resisting properties they are unsuitable in the manufacture of window glass substitutes such as referred to herein.

It is to be understood that although a preferred embodiment is shown, such modifications as above set forth or others may be made therein without departing from the spirit and scope of the invention as set forth in the appended claims.

What is claimed is:

1. As an article of manufacture the combination with areticular metallic base material of, a flexible film formed by evaporation of a thin solution of a cellulose ester and a plasticizer adapted to pass ultraviolet light in the region most beneficial biologically, and also capable of imparting weather resistant properties of the film.

2. As an article of manufacture the combination with a reticular metallic base material of, a flexible film formed by evaporation of a thin solution of a cellulose ester and a plasticizer adapted to pass ultraviolet light substantially restricted to waves longer than 2800 A., and also capable of imparting weather resistant properties of the film.

3. As an article of manufacture the combination with a reticular metallic base material. of, a flexible film formed by evaporation of a thin solution of a cellulose ester and a plasticizer, the transparency of which film for visible light is.about and which transmits sunlight substantially unaltered.

4. An article of manufacture comprising a thin, transparent film formed by the evaporation of a solution containing cellulose acetate and diethylphthalate in a low boiling solvent, the proportions of said ingredients being such that the resulting film transmits light of the ultraviolet spectrum between 3200 and 2800 A. and absorbs those rays of a shorter wave length.

5. An article of manufacture comprising a thin transparent film formed by the evaporation of a solution containing cellulose acetate and diethylphthalate in a low boiling solvent, the proportions of said ingredients being such that the film absorbs all rays of light having a wave length shorter than substantially 2800 A. but transmits about 40% of the rays having longer wave length.

6. As an article of manufacture the combi nation with a reticular metallic base material of, a flexible film formed by evaporation of a thin solution of a cellulose ester and a plasticizer, said film having inherent weather resisting properties due to its ability to wet the strands of the base and follow the expansion and contraction thereof, and said film being adapted to pass ultraviolet light in the region most beneficial biologically.

7. As an article of manufacture the combination with a reticular metallic base material of, a flexible film formed by evaporation of a thin solution of a cellulose ester and a plasticizer, each of said constituent-s being adapted to pass ultraviolet light in the region most beneficial biologically, and the plasticizer being adapted to perform the following functions with respect to the film (a) impart elasticity thereto and (6) cause the film to wet the strands of the base and follow the expansion and contraction thereof; whereby said film has sulficient durability to give a commercially satisfactory life when the article is used as a glass substitute.

8. As an article of manufacture the combination with a reticular metallic 'base material of, a flexible film formed by evaporation of a thin solution of a cellulose ester and a plasticizer, said film being characterized by its ability to transmit ultraviolet light within the band of rays covering the range of 3200 A. to 2800 A. and absorbing those rays shorter than 2800 A., and said film having sufficient durability to resist exposure to the weather so as to have a commercially satisfactory life when the article is used as a glass substitute.

In testimony whereof, I have hereunto subscribed my name this eighth day of February,

. ADOLPI-I ZIMMERLI. 

